Dinesh Kulkarni has written a nice post about RIA Services (Alexandria) roadmap:

http://silverlight.net/forums/p/101160/230835.aspx#230835

So, RIA Services milestones are:

- July 2009 CTP
 
- PDC 2009 Beta (November) 

- First part of 2010: RTW (Like .NET 4.0)

Another key point is that we might provide support for .NET 3.5 SP1 in the server (where you run RIA Services), not just .NET 4.0. I think it is a good point for many customers who are not so agile to rapidly change to .NET 4.0. I just want to highlight that I say 'we might'. This is just a possibility, it is not a final commitment. :-)